The terms "mixing" and "stirring" should be understood as covering any pure mixing operation between at least two ingredients which are to be homogenized, together with any operation having the purpose of changing the state of one or more basic substances or one or more compounds by reacting under various ambient conditions of pressure, temperature, or interaction, with or without modification of ambient conditions.
Of the numerous applications that may be envisaged, it is appropriate to mention the fabrication of raw materials, the preparation of industrial substances such as paint, polymers, glue, plastics, the fabrication of chemical substances which are purely and solely industrial in character, or foodstuffs, or pharmaceutical substances.
Substances or compositions which are in powder, paste, or granular form are stirred or agitated inside receptacles, vats, or enclosures which are generally closed having a drive shaft passing locally therethrough with a moving agitator member constituting a hub and a given number of blades fixed thereon.
Various forms of vat have been adopted for performing such an operation, and the corresponding agitator members are appropriately shaped, generally to ensure that the blades move as close as possible to the corresponding portions of the inside face of the vat.
The following patent documents are mentioned by way of example: DE-A-25 25 362, EP-A-O 131 885, and U.S. Pat. No. 2 982 522.
Experience shows that presently available apparatuses leave room for improvement concerning the functions of stirring, kneading, mixing, or homogenizing the substances that they are to work on.
A first such possibility relates to the profile of the blades for improving energetic stirring of substances contained in the receptacle or vat of the apparatus while avoiding setting up preferred lines of motion. It has been observed that the varying number of blades on the agitator cannot solve this problem, which must be solved as a function of the particular shape of the blades.
Another object of the invention is to improve blade strength in the face of intense mechanical forces which increase with increasing drive torque and with increasing viscosity of the substances to be stirred.
Another object is to regulate the internal or core temperature of the substances or the composition being stirred either in order to prevent an increase in temperature due to stirring friction or else, in contrast, to add or remove heat so as to encourage an intimate reaction under an atmosphere which may be inert or reactive.
The present invention seeks to achieve the above objects by proposing a novel moving agitator member designed to:
further improve energetic stirring and homogenization of substances being treated, be they substances in powder, paste, or granular form;
considerably increase the mechanical strength of the blades, thereby enabling a high level of torque to be transmitted even within a mass of paste, powder, or liquid having a high level of viscosity; and
enable narrower temperature regulation within the core of the substances being kneaded or mixed by virtue of blades which also operate as heat exchangers.